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(Sub)mm & Infrared
Spectroscopy of
Circumstellar Disks
HD 141569A
(HST ACS)
Geoffrey A. Blake
Div. Geological & Planetary Sciences
59th OSU Symposium
25June2004
People Really Doing the Work!
Caltech:
-Jacqueline Kessler (now at UT Austin), Joanna Brown
-Adwin Boogert, Chunhua Qi (now at the SMA/CfA)
Leiden w/Ewine van Dishoeck & Michiel Hogerheijde:
-Klaus Pontoppidan, Gerd Jan van Zadelhoff,
Wing-Fai Thi (now at ESO)
I.
II.
III.
IV.
Why study disks?
Mm-wave interferometry of protoplanetary disks.
High resolution IR spectroscopy of disks.
Conclusions
25June2004
How are isolated Sun-like stars formed?
outflow
x1000
in scale
Cloud collapse
Planet formation
infall
Rotating disk
Mature solar system
Picture largely derived from indirect tracers, especially SEDs.
Adapted from McCaughrean
Spitzer Space Telescope
- IRAC (mid-IR cameras, 3.6
4.5, 5.8, 8.0 mm)
- MIPS (far-IR cameras, 24, 70
160 mm, R=20 SED mode)
- IRS (5-40 mm long slit,R=150,
10-38 mm echelle, R=600)
August 2003 launch,
>5 year lifetime.
- GTO observations
- Legacy program
Evans et al., c2d
~170 YSOs first look +
follow up of mapping.
Meyer et al.
Photometry~350 sources,
IRS follow up (Class III).
- General observations
25June2004
Ices toward young low mass stars
HH 46 w/IRAC, IRS
Keck/VLT
+Spitzer
Boogert et al. 2004, ApJS special issue
25June2004
Study Isolated Disks (Weak/No Outflow)
Planet
building
phase
Beckwith & Sargent 1996, Nature 383, 139-144.
25June2004
Why study disks? Star-disk-planet interactions:
Radial velocity surveys are
sensitive to ~Jupiter/Saturn
mass planets out to >5 AU.
From whence hot-Jupiters?
The answer lies at earlier times…
Disk-star- and
protoplanet
interactions lead
to migration
while the disk is
present.
Theory
1 AU at 140 pc
subtends 0.’’007.
Jupiter (5 AU):
V_doppler = 13 m/s
V_orbit = 13 km/s
Simulation G. Bryden
Observation?
Spectroscopy of “Disk Atmospheres”
G.J. van
Zadelhoff
2002
Chiang &
Goldreich
1997
IR
disk surface within several – several tens of AU
(sub)mm
disk surface at large radii, disk interior
25June2004
The 1-Baseline Heterodyne Interferometer:
Geometrical delay
•HST resolution at 1mm
D=10 km! Use array.
•Can’t directly process 100 –
1000 GHz signals.
•Heterodyne receivers detect
|V| and f, noise defined by
the quantum limit of hn/k.
•Positional information is
carried by the PHASE.
•Spectral coverage depends
on the receivers, while the
kinematic resolution is
determined by correlator.
25June2004
The n-Element Heterodyne Interferometer:
•n(n-1)/2 baselines,
imaging performance
depends on the array
geometry, but
•For small to moderate
n, the (u,v) plane is
sparsely filled.
•For a given array, the
minimum detectable
temperature varies as
(resolution = qS)-2 :
qP = primary telescope beam
25June2004
CO traces disk geometry, velocity field:
CO 3-2
TW Hydra w/SMA
CO 2-1
Qi et al. 2004,
ApJL, in press.
Disk Ionization Structure: CO and Ions
Disk properties vary widely
with radius, height; and
depend on accretion rate,
etc. (Aikawa et al. 2002, w/
D’Alessio et al. disk models).
Currently sensitive only to R>80 AU
in gas tracers, R<80 AU dust.
CO clearly optically thick, isotopes reveal
extensive depletion, poor mass tracer!
The fractional ionization is >10-8, easily
sufficient for MRI transport. HD & H2D+
(Ceccarelli et al. 2004) in midplane?
Chemical Imaging of Outer Disk?
Qi et al. 2004
& in prep
HDO formed via H2D+,
possible tracer of H3+?
Kessler et al.
2004, in prep
(6 transits)
CO well mixed, while
[CN]/[HCN] traces
enhanced UV fields.
Is LkCa 15 unusual?
Photodesorption?
Molecular Distribution Models
LkCa 15
HCN observations
For models:
Using scaled H density distribution NT
with varying inner radius cutoff
Ro=50AU
Ro=100AU
R0
Rout
Ro=200AU
Ro=300AU
Transitional/Debris Disks?
HD141569 & Vega w/PdBI:
Vega, Wilner et al. 2002
CO 2-1 from HD141569
J.-C. Augereau & A. Dutrey
astro-ph/0404191
Future of the U.S. University Arrays – CARMA
CARMA = OVRO (6 10.4m) + BIMA (9 6.1m) + SZ Array
(8 3.5m) telescopes.
March 27th , 2004
SUP approved!
2004 SZA at OVRO
2004 move 6.1m
2004 move 10.4m
2005 full operations
Cedar Flat 7300 ft.
June 15th, 2004
How can we probe the planet-forming region?
Theory
(pre-ALMA) The
size scales are too
small even for the
largest current &
near-term arrays.
Spectroscopy to
the rescue!
Jupiter (5 AU):
V_doppler = 13 m/s
V_orbit = 13 km/s
Observation?
High Resolution IR Spectroscopy & Disks
R=10,000-100,000 (30-3 km/s) echelles
(ISAAC,NIRSPEC, PHOENIX,TEXES)
on 8-10 m telescopes can now probe
“typical” T Tauri/Herbig Ae stars:
Keck
CO M-band fundamental
AB Aur
NIRSPEC
R=25000
HD 163296
Orientation is Pivotal in the IR!
Edge-on
absorption.
L1489:
Gas/Ice~10/1,
accretion.
CRBR2422.8:
Gas/Ice~1/1,
velocity field?
Elias 18
Gas/Ice<1/10
(Shuping et al.)
25June2004
H2, H3+ in absorption?
Spitzer Enables the Study of Edge-on Disks!
VLT
The small molecules in ices are
similar in protostars and disks.
25June2004
Flux (Jy)
VLT
ISAACS
What about other species w/echelles?
NGC 7538 IRS9
Boogert et al. 2004, ApJ, in press
25June2004
Edge-on Disks & Comets?
N7538 W33A Hale-Bopp
Water
100
100
100
CO
10
1
23
CO2
16
3
6
CH4
1
0.7
0.6
H2CO
3
2
1
CH3OH
9
10
2
HCOOH
2
0.5
0.1
NH3
10
4
0.7
OCS
0.1 0.05
0.4
IR studies of edge on disks will map out both gas phase & grain
mantle composition, compare to that found in massive YSOs, comets.
25June2004
In older systems, CO disk emission is common:
Herbig Ae stars, from
~face-on (AB Aur) to highly
inclined (HD 163296).
CO lines correlated with
inclination and much narrower
than those of H I
Disk!
CO lines give distances slightly larger
than K-band interferometry, broad H I
traces gas much closer to star (see also
Brittain & Rettig 2002, ApJ, 588, 535;
Najita et al. 2003, ApJ, 589, 931).
Can do ~30-40 objects/night.
Pf b
Systematic Line Width Trends:
•Objects thought to be ~face
on have the narrowest line
widths, highly inclined
systems the largest.
•As the excitation energy
increases, so does the line
width (small effect).
•Consistent with disk
emission, radii range from
0.5-5 AU at high J.
•Low J lines also resonantly
scatter 5 mm photons to
much larger distances.
•Asymmetries (VV Ser)?
Blake & Boogert 2004, ApJL 606, L73.
25June2004
How is the CO excited in these disks?
CO
13
CO
CO and 13CO rotation diagrams
show curvature as a result of
t>1. Still, small amounts of gas
since N(H2)~5 x 1022 leads to
dust opacities near unity.
Collisional excitation important,
but cannot explain line widths
at low J values (too broad).
Resonant IR scattering
at larger radii!
The vibrational excitation is
highly variable, likely due to
variations in the UV field.
Disk shadowing?
25June2004
Where does the CO emission come from?
Flared disk models often possess
2-5 micron deficiency in model
SEDs, where a “bump” is often
observed for Herbig Ae stars.
Dullemond et al. 2002
Explanation:
Dust sublimation near
the star exposes the
inner disk to direct
stellar radiation,
heating the dust and
“puffing up” the disk.
25June2004
CO Emission from Disks around T Tauri Stars
For dust sublimation
alone, the lines from T
Tauri disks should be
broader than those from
Herbig Ae stars+disks.
Often observed, but…
Calvet et al. 2002
The TW Hya lines are extremely
narrow, even for a disk with i~7
degrees, imply R>2 AU. Gap tracer?
Disk Spectroscopy - Conclusions
AB Aur
(Sub)mm-wave instruments can only study the
outer reaches of large disks at present in lines;
even at these wavelengths the disk mid-plane is
largely inaccessible due to molecular depletion.
Expanded arrays (CARMA, eSMA, ALMA)
will provide access to much smaller scales,
lines should selectively highlight regions of
planet accretion/formation. Midplane w/H2D+?
HD 163296
High resolution IR spectroscopy just starting,
is immensely powerful, and provides unique
access to the 0.5-50 AU disk surface before
advent of ALMA, large IR interferometers.
Spectra are esp. sensitive to disk geometry.
Spitzer is providing beautiful spectrophotometric
SEDs and many new targets!
25June2004
Arrays everywhere!
PdBI
VLA
BIMA
SMA
ATCA
OVRO
Typically ntel ≤ 6-10.
25June2004
Embedded disks?
3mm: HCO+, HCN, 13CO, C180 (1-0)
 2000 AU radius, 0.02 M disk
1mm: HCO+ (3-2)  infall (disk not
quite fully rotationally supported)
0.65 M  M  1.4 M
disk collapse to 300 AU in 2 x 104 yrs?
L1489, a disk in transition?
HCO+ 3-2
Hogerheijde 2001
HCO+ 1-0
Padgett et al 1999
See also:
Hogerheijde et
al 1997, 1998;
Looney 2000;
Chandler & Richer
2000, Shirley et al
2000
OVRO CO(2-1) Survey of T Tauri stars
(Koerner & Sargent 2003)
• stellar ages 1 - 10 Myrs
• stellar masses ~ 1 M
• selection by 1 mm flux, SED
characteristics
• Taurus 19/19 detections
• Ophiuchus 4/6 detections
• resolution ~ 2”
20 objects
radii  150 AU
masses  0.02 M
(from SEDs)
See also Dutrey, Guilloteau,
& Simon, Ohashi
Understanding Disk Chemistry
Molecular line survey
UV fields
grain reactions
disk ages and evolution
Chemical / Radiative Transfer Modeling
Physical model: D'Alessio et al. 2001
Chemical model: Willacy& Langer 2001
Radiative transfer: Hogerheijde & vander Tak 2000
MM-Wave CO Traces Dynamics, Others?
D. Koerner & A.
Sargent OVRO, in
Qi et al. (2004).
Measure:
R_disk
M_star
Inclination
w/resolved
images.
Dutrey et al. 1997, IRAM 30m
LkCa 15
15
LkCa
25June2004
OVRO+CSO/JCMT MM-Wave Disk Survey
The Sample (drawn from larger single dish + OVRO CO survey):
Star
Sp Type
LkCa 15
K5:V
GM Aur
K5V:e
HD 163296 A0
MWC 480 A3
d(pc) Teff(K) R(Rsun) L(Lsun) M(Msun) Age(Myr)
140
4365
1.64
0.72
0.81
11.7
140
4060
1.78
0.8
0.84
1.8
120
9550
2.2
30.2
2.3
6.0
130
8710
2.1
32.4
2.0
4.6
MWC 480
LkCa 15
Mannings, Koerner & Sargent 1997
Koerner & Sargent 1995
25June2004
OVRO+CSO/JCMT MM-Wave Disk Survey II
van Zadelhoff et al. 2001
Combine 3/1.3 mm array images w/higher J spectra to
constrain OUTER disk properties, chemical networks.
25June2004
UV Fields: HCN and CN
Source
L* (L)
LkCa 15
0.72
GM Aur
0.80
MWC 480
30.2
HD 163293 35.2
CN/HCN Hdust/hgas
~ 10
1.0
<< 1
4.0
~4
1.7
>> 50
LkCa 15
Molecular distribution
ring-like?
Photochemistry
or desorption?
Qi et al., in prep
25June2004
[CN]/[HCN] traces
enhanced UV fields
(Fuente et al. 1993,
Chiang et al. 2001)
Modeling the effects of (uv) Sampling
Model Parameters
i = 58°, Vturb= 0.1 km/s
Ro= 5 AU, Rout= 430 AU
nCO = 10-4 nH (D'Alessio 2001)
qsyn = 3.6” x 3.6”
9.5
8.9
8.2
7.6
6.9
5.6
5.0
4.3
3.7
3.0
Infinite resolution, complete UV coverage
LkCa15 ___
model - - -
CO 2-1 fit
Observed UV sampling, uniform weighting
6.3
Are these large disks unusual?
CO, HCO+ (and
NNH+) chemistry
well predicted by
disk models.
Other species, esp.
CS, CN, HCN, much
more intense, with
unusual emission
patterns in some
cases (LkCa 15).
MM-continuum surveys do not reveal such large,
massive disks in similarly aged clusters (IC348)
and clouds (NGC 2024, MBM12). Environment?
Need better (sub)mm-wave imaging capabilities. SMA! and…
29Aprn03
CARMA – Site Monitoring
Disk Observations w/CARMA+ALMA
CARMA
ALMA
Md=0.01Msun Rout=120AU Ro=20AU
HDO:
rms (3sigma) = 0.05-0.1 K
(CARMA w/D config. in 4 hrs)
Dust simulation (L.G. Mundy), unrealistic
phase errors, but no CLEAN/MEM.
Atmospheric Phase Correction (mm Adaptive Optics)
•Atm. fluctuations (mostly
H2O) can vary geom. delay.
•|V|eif
decorrelation
if Ef>p (each baseline).
•If the fluctuations vary
systematically across the
array, phase errors ensue.
•Problem is NOT solved.
OVRO WLM
System
Enter ALMA:
Dust simulation (L.G. Mundy), unrealistic
phase errors, but no CLEAN/MEM.
Superb site & large
array
exceptional
performance (64 12m
telescopes, by 2012).
Llano de
Chajnantor; 5000
m, good for
astronomy, tough
for humans!
Ices in the disk of L1489 IRS
•
Prominent band of solid CO
detected toward L1489,
originating in large, flaring disk.
• CO band consists of 3
components, explained by
laboratory simulations as
originating from CO in 3 distinct
mixtures:
1 'polar' H2O:CO
2 'apolar' CO2:CO
[NEW!]
3 'apolar' pure CO
(Boogert, Hogerheijde & Blake, ApJ 568,761, 2002)
Variations in CO M-band Spectra:
Nearly all spectra
observed to date have
emission from very high
J levels (J>30-35), but…
The degree of vibrational
excitation is highly variable!
25June2004
SED Fits versus IR Interferometry
Fits to AB Aur SED yield an
inner radius of ~0.5 AU (and
0.06 AU for T Tau).
(Monnier & Millan-Gabet 2002, ApJ)
Dullemond et al. 2002
This model can now be
directly tested via YSO
size determinations with
K-band interferometry.
Intense dust emission pumps
CO, rim “shadowing” can
produce moderate T_rot.
Future “Near”-IR (1-5 mm) Spectroscopy
Brittain & Rettig 2002, Nature
Many other species and disk types
(transitional, debris, etc.) should be
examined in both absorption (edge-on
disks) and emission, but extremely
high dynamic range will be needed.
Protoplanet tracers?
H2, H3+, CH4, H2O, OCS...
Line profile asymmetries?